The present invention relates to an optical disk recording/reproducing apparatus and an optical disk recording/reproducing method and, more particularly, to an optical disk recording/reproducing technique which enables an apparatus to speed up a process of restarting a recording from a position on which a reproduction was once interrupted.
A pregroove having a spiral pattern, which functions as a guide groove, is formed on recordable optical disks such as a CD-R disk. Since the guide groove winds with a deviation in the radial direction of about ±0.03 μm and at a cycle of 54 to 63 μm, an FM wave having a center frequency of 22.05 kHz and a frequency shift of ±1 kHz is detected when the disk is rotated at a constant linear velocity of, for example, 1.3 m/s (hereinafter, the FM wave produced by the wobbling is referred to as “wobble signal”). The wobble signal contains frequency-modulated ATIP (Absolute Time In Pregroove) address information indicating absolute time information of the disk, frequency-modulated recording control information, and so forth. At the time of a recording, information such as the ATIP address information, setting information of recording conditions, and so forth of the optical disk is reproduced from the wobble signal to be used for controlling the drive.
Data-recording on the CD-R disk is performed by: reading out the ATIP address from the pregroove; adding the ATIP address position information to the data which is inputted externally by the use of an encoder; executing EFM (Eight to Fourteen Modulation) modulation processing; and irradiating the optical disk with laser light for recording.
In turn, in the case of an occurrence of a so-called buffer underrun, i.e., when a lack of data to be written on the optical disk comes short during the recording operation of the optical disk because a speed of writing data on the optical disk is faster than that of transferring data from a host computer, the data-writing on the optical disk is interrupted so that a predetermined quantity of data, which is transferred from the host computer, is accumulated in a buffer RAM, and then the data-recording on the optical disk is restarted.
In order to restart the data-writing on the optical disk from the position on which the data-recording was interrupted, speed information of the optical disk and the ATIP address information at the time of the interruption are required. However, in the conventional CLV (Constant Linear Velocity) method where data is recorded at a constant linear velocity, the recording speed is constant in the whole area of from the inner periphery to the outer periphery. A recording speed in the conventional ZCLV (Zone Constant Linear Velocity) recording method is set to be constant in identical zones. Therefore, a parameter of the recording speed (fixed value) has been used as the rotation speed of the optical disk from which the EFM signal is reproduced, the EFM signal being used for detecting information of the position, from which a pickup starts tracing on the optical disk in advance of the restart of recording.
But, due to the increase in the speed of recording data on the optical disk, there has been a shift from the CLV recording methods to the CAV (Constant Angular Velocity) recording method which enables to further reduce the recording time. Since the angular velocity is constant in the CAV recording method, the recording speed changes constantly in accordance with a disk radius; therefore, the conventional method of using the parameter of the fixed value as the optical disk speed setting in reproducing the EFM signal at the time of restarting the data-recording after the buffer underrun protection is no longer usable. Thus, there is a demand for establishing new ways for recognizing the reproduction speed setting of the optical disk.
Japanese Patent Laid-open No. 2002-222561 discloses a method of performing a recording/reproducing operation by switching from the CAV recording to the CLV recording at the time of restarting a recording when the recording has been interrupted in order to avoid the buffer underrun, etc. in the CAV recording.